C ++代碼的意外輸出

Question

好的，伙計們...我只是想在這里練習結構，我編寫了以下C ++代碼：

#include <iostream>
#include <cstring>

using namespace std;

struct DATE {
    int year;
    int month;
    int date;
};
struct Book {
    char name[50];
    char author[50];
    int id;
    DATE date;
};

int main() {
     Book book1;
     DATE date1;
     char bookName, bookAuthor,*bookNamePointer = "", *bookAuthorPointer = "";
     int date, year, month;

     cout << "Date Of Publishing? " << endl;
     cin >> date;
     cout << "Month Of Publishing?" << endl;
     cin >> month;
     cout << "Year Of Publishing?" << endl;
     cin >> year;
     date1.year = year;
     date1.month = month;
     date1.date = date;

     cout << "Book Name ? " << endl;
     cin >> bookName;

     printf("********** \n");

     cout << "Book Author ? " << endl;
     cin >> bookAuthor;



     strcpy_s(book1.name, &bookName);
     strcpy_s(book1.author, &bookAuthor);
     printf("Book Name %s \n", book1.name);
     printf("Book Author %s \n", book1.author);
    return 0;
}

好吧，顯然，這里用戶只是輸入書名，作者名，依此類推...做到了，但是當我到達輸入書名作者的那一刻，我就停了下來。我的printf（）最奇怪的答案； 我還沒有看到這樣的怪事。 我想我將需要展示一張圖片（沒有警告或錯誤）：

編輯

在我使用std :: string ....之后

#include <iostream>
#include <cstring>
#include <string>

using namespace std;

struct DATE {
    int year;
    int month;
    int date;
};
struct Book {
    char name[50];
    char author[50];
    int id;
    DATE date;
};

int main() {
     Book book1;
     DATE date1;
     std::string bookName, bookAuthor;
     int date, year, month;

     cout << "Date Of Publishing? " << endl;
     cin >> date;
     cout << "Month Of Publishing?" << endl;
     cin >> month;
     cout << "Year Of Publishing?" << endl;
     cin >> year;
     date1.year = year;
     date1.month = month;
     date1.date = date;

     cout << "Book Name ? " << endl;
     cin >> bookName;

     printf("********** \n");

     cout << "Book Author ? " << endl;
     cin >> bookAuthor;



    /* strcpy_s(book1.name, &bookName);
     strcpy_s(book1.author, &bookAuthor);
     printf("Book Name %s \n", book1.name);
     printf("Book Author %s \n", book1.author);*/
    return 0;
}

我實際上沒有輸入Book Author ..它只是停止了。 並說按一個鍵繼續...請幫助！

編輯2

#include <iostream>
#include <cstring>

using namespace std;

struct DATE {
    int year;
    int month;
    int date;
};
struct Book {
    char name[50];
    char author[50];
    int id;
    DATE date;
};

int main() {
     Book book1;
     DATE date1;
     int date, year, month;

     cout << "Date Of Publishing? " << endl;
     cin >> date;
     cout << "Month Of Publishing?" << endl;
     cin >> month;
     cout << "Year Of Publishing?" << endl;
     cin >> year;
     date1.year = year;
     date1.month = month;
     date1.date = date;

     cout << "Book Name ? " << endl;
     cin >> book1.name;

     cout << "Book Author ? " << endl;
     cin >> book1.author;

     cout << "Book Author: " <<book1.author << endl;
     cout << "Book Name: " << book1.name << endl;
     cout << "Date : " << book1.date.month << "/" << book1.date.date << "/" << book1.date.year;

    return 0;
}

我幾乎可以處理所有內容，但我可以輸入作者的文字！！！ 請看一下圖片，以更具描述性：

解

#include <iostream>
#include <cstring>



struct DATE {
    int year;
    int month;
    int date;
};
struct Book {
    char name[50];
    char author[50];
    int id;
    DATE date;
};

int main() {
     Book book1;
     DATE date1;

     std::cout << "Date Of Publishing? " << std::endl;
     std::cin >> book1.date.date;
     std::cout << "Month Of Publishing?" << std::endl;
     std::cin >> book1.date.month;
     std::cout << "Year Of Publishing?" << std::endl;
     std::cin >> book1.date.year;


     std::cout << "Book Name ? " << std::endl;
     std::cin >> book1.name;

     std::cout << "Book Author ? " << std::endl;
     std::cin >> book1.author;

     std::cout << "Book Author: " <<book1.author << std::endl;
     std::cout << "Book Name: " << book1.name << std::endl;
     std::cout << "Date : " << book1.date.month << "/" << book1.date.date << "/" << book1.date.year << std::endl;

    return 0;
}

Answer 1

char表示一個字符。 bookName是一個字符。 cin >> bookName; 存儲您鍵入的第一個字符，並且僅存儲該第一個字符。

然后strcpy_s(book1.name, &bookName); 導致未定義的行為，因為最后一個參數應該指向字符串，但是您提供了指向單個字符的指針。

另外，您對strcpy_s使用了錯誤數量的參數，編譯器應對此發出警告。 在運行程序之前，請務必修復所有編譯器警告/錯誤。 對於printf還應該有一個#include 。

bookAuthor有類似的問題。 要解決這些問題，請停止使用chars和char數組。 使用#include <string> ，然后使用std::string代替。

Answer 2

您將bookName和bookAuthor定義為一個字母，即一個字符。 通過使用：

cin >> bookName; 

您僅讀取一個字符，其余行仍在緩沖區中，將在下一個輸入操作中讀取。 您應該使用string標頭（ #include <string> ）中定義的std::string類型定義這些變量。

struct Book {
    string name;
    string author;
    int id;
    DATE date;
};

和

string bookName, bookAuthor;

但是您仍將只讀一個單詞，沒有前導空格或任何空格字符，以讀取到行尾，您需要使用std::getline ：

getline( cin, bookName ); // read to the end of line, without new line char
book1.name = bookName; //simply copy string by assing

Answer 3

僅供參考！

通常在C ++中更喜歡cout和cin而cin printf 。 另外，您無需擔心此處的std::string只需直接讀取該結構即可。

#include <iostream>
#include <cstring>

struct DATE 
{
   int Year;
   int Month;
   int Date;
};

struct Book 
{
   char  Name   [50];
   char  Author [50];
};


int main() 
{
   Book Book1;
   DATE Date1;

   std::cout << "Date Of Publishing? " << std::endl;
   std::cin >> Date1.Date;
   std::cout << "Month Of Publishing?" << std::endl;
   std::cin >> Date1.Month;
   std::cout << "Year Of Publishing?" << std::endl;
   std::cin >> Date1.Year;

   std::cout << "Book Name ? " << std::endl;
   std::cin >> Book1.Name;

   std::cout << "********** \n";

   std::cout << "Book Author ? " << std::endl;
   std::cin >> Book1.Author;

   std::cout << "Book Name \n" << Book1.Name << std::endl;
   std::cout << "Book Author \n" << Book1.Author << std::endl;
   return 0;
}